Load animation speed from new global animation speed controller
It doesn't belong with advanced compositing settings as it's quite user
friendly, and we also want to adjust other animation speeds. May as well
do it together.
In the current form all compositing is still completely reinitiliased
like with the previous slider. Change notifications come in the form of
KConfigWatcher rather than our own bespoke update interface.
Moved new slider, minimised a window.
It still behaved as expected.
Reviewers: KWin, zzag
Reviewed By: KWin, zzag
Subscribers: zzag, broulik, anthonyfieroni, kwin
Differential Revision: https://phabricator.kde.org/D22887